title: Effects of cadmium on the expression of placental lactogens and Pit-1 genes in the rat placental trophoblast cells.
abstract: Cadmium is an endocrine disrupter (ED) with detrimental effects on mammalian reproduction. The placenta is a primary target for cadmium toxicity during pregnancy. Very little of this metal crosses the placenta to the fetus, and consequently it accumulates in high concentrations in the placenta. Cadmium affects on steroid synthesis and has estrogen- and androgen-like activities. In this study, we investigated the toxic effects of cadmium on placental trophoblast cells as well as the mRNA levels of placental lactogens (PLs), which are under the control of estrogen and play a pivotal role during pregnancy. Pregnant F344 Fisher rats were injected subcutaneously with 0, 0.2, and 2.0mg/kg BW/day of cadmium (CdCl(2)) dissolved in saline from days 11 to 19 of pregnancy and were sacrificed on day 20. The mRNA levels of the PL-Iv and -II genes and Pit-1alpha and beta isotype genes, the trans-acting factor of PLs, were analyzed by Northern blot hybridization and reverse transcription-polymerase chain reaction, respectively. The frequency of the placental trophoblast cells was observed histochemically. Developmental data and apoptotic chromosomal DNA fragmentation of placental cells were also observed. The mRNA levels of PL-Iv and -II were reduced in a dose-dependent manner by cadmium. The mRNA levels of the Pit-1alpha and beta isotype genes were also reduced by cadmium. In the uterus-conjugated region of the placental junctional zone, the frequency rates of trophoblast cells were lower in the cadmium-treated groups than in the control group. High-dose cadmium exposure (2.0mg) induced not only the reduction of trophoblast cell frequency but also apoptotic chromosomal DNA fragmentation in the junctional zone of the placenta. Developmental metrics such as placental and fetal weights and a number of live fetuses, decreased, while a numbers of resorptions, dead fetuses, and post-implantation losses increased significantly (p<0.05) in the cadmium-treated groups compared to the control. These data suggested that cadmium inhibits the expression of PL genes and reduces the number of trophoblast cells in the rat placenta via an estrogen-like activity, leading to significant toxic effects on placental growth and physiological function in rats.
authors.affiliation: Institute of Environmental and Occupational Medicine, Department of Occupational and Environmental Medicine, Busan Paik Hospital, Inje University, Busan 614-735, Republic of Korea.
authors.forename: Chae Kwan
authors.initials: CK
authors.lastname: Lee
authors.forename: Jong Tae
authors.initials: JT
authors.lastname: Lee
authors.forename: Seong Jin
authors.initials: SJ
authors.lastname: Yu
authors.forename: Sung Goo
authors.initials: SG
authors.lastname: Kang
authors.forename: Chan Seok
authors.initials: CS
authors.lastname: Moon
authors.forename: Young Ha
authors.initials: YH
authors.lastname: Choi
authors.forename: Jeong Ho
authors.initials: JH
authors.lastname: Kim
authors.forename: Dae Hwan
authors.initials: DH
authors.lastname: Kim
authors.forename: Byung Chul
authors.initials: BC
authors.lastname: Son
authors.forename: Chang Hee
authors.initials: CH
authors.lastname: Lee
authors.forename: Hwi Dong
authors.initials: HD
authors.lastname: Kim
authors.forename: Jin Hong
authors.initials: JH
authors.lastname: Ahn
mesh_terms: D000818:Animals; D002104:Cadmium / Q000494:pharmacology* / Q000633:toxicity; D002452:Cell Count; D015536:Down-Regulation / Q000187:drug effects; D010064:Embryo Implantation / Q000187:drug effects / Q000235:genetics; D005260:Female; D005328:Fetal Viability / Q000187:drug effects; D005786:Gene Expression Regulation / Q000187:drug effects; D010920:Placenta / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010928:Placental Lactogen / Q000235:genetics* / Q000378:metabolism; D011247:Pregnancy; D011388:Prolactin / Q000235:genetics; D051381:Rats; D011916:Rats, Inbred F344; D050817:Transcription Factor Pit-1 / Q000235:genetics* / Q000378:metabolism; D014327:Trophoblasts / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D050817:Transcription Factor Pit-1; D002104:Cadmium; D011388:Prolactin; D010928:Placental Lactogen